Tuning arrangement for electric oscillations



July 8, 1941. w. PUHLMANN EI'AL TUNING ARRANGEMENT FOR ELECTRICOSCILLATIONS Filed Oct. 8, 1938 a X mm PM .1 a m.

Patented July 8, 1941 TUNING ARRANGEMENT FOR ELECTRIG OSCILLATIONSWerner Puhlmann and Erich Gossel, Berlin, Germany, assignors to C.Lorenz Aktiengesellschaft, Eerlin-Tempclhof, Germany, a companyApplication October 8, 1938, Serial No. 233,924 In Germany October 19,1937 2 Claims.

In circuit arrangements for very short waves, especially those of thedecimeter range, it is Well known to employ an inductance connected directly to the grid and anode of an. electron tube. Such arrangements arein the nature of threepoint feedback connections of the kind in whichthe capacities of the oscillatory circuits are constituted by theinter-electrode capacities. The inductance of the circuit is a bail, forinstance, having tubular member one of which is arranged to slide in theother after the manner of a trombone slide, thus providing for theadjustment of the inductance.

Tuning arrangements of this type have the disadvantage that the surfacesof contact of the said bail members allow high frequency currents toflow through the bail, whereby through variation of the transition orcontact resistance losses are easy to occur in the circuit.

For the avoidance of this drawback the invention in order to provide forfrequency adjustment proposes to fit such a bail-shaped inductance witha displaceable conductive body by which the electric properties of thebail circuit are influenced, this being probably due to ca pacitivedetuning.

The invention will be understood from the following description,reference being had to the accompanying drawing, in which Fig. 1 showsthe well known circuit arrangement of devices of this kind, Fig. 2 is apartially sectioned view of a tuning arrangement as provided by theinvention, Fig. 3 shows a section on line 3-3 of Fig. 2.

In the arrangement represented in Fig. 1 an oscillatory circuit 2 isjoined to the grid and anode of a three-electrode tube I. This circuitis interrupted in direct-current fashion by a condenser 3 in order tosupply to the tube an adjustable anode voltage from A and an adjustablegrid voltage from G. The grid voltage is supplied over a resistance 4.

As the capacity of the oscillatory circuits is substantially defined bythe inter-electrode capacity, a frequency adjustment is obtained byinfluencing the inductance. Such influence, as stated before, is inaccordance with the invention effected by varying the position of aconductive body with respect to this inductance. In the case of Figs. 2and 3 such conductive body 6 is a solid metal body fastened to aninsulating body I. The bodies 6, 1 are carried by a set screw 8 havingits thread engaged by thread provided in a support 9 made of aninsulating material. Screw 8 is rotatably secured in body 1. This isguided in the cross bar of a bail it, being seated in an aperture 5thereof. Bail i4 is a solid metal body of rectangular cross section.

Since in thi way body 6 does not contact with the bail I4, that servesas the said inductance, any difficulties arising through such contactare avoided. The electron tube I may be mounted on bail l4.

By rotating the screw 8 the assembly 1, 6 can be displaced within thebail to effect the desired frequency adjustment.

With an arrangement of this kind and a wavelength of 50 centimeters, forinstance, it has been possible to obtain a frequency variation amountingto +10 per cent.

What is claimed is:

1. A tuning arrangement for electric oscillations comprising anoscillatory circuit, a metallic generally U-shaped inductance havingparal lel sides and a cross bar provided with a noncircular apertureincluded in said oscillatory circuit, a non-circular insulating bodyfitting in said aperture to resist rotation while allowing slidingmovement, a 1C1'OSS bar supported on said body and extending across saidU-shaped inductance from one parallel side to the other but out ofcontact with both said sides, screw means for sliding said insulatingbody through said aper ture parallel to said sides of said U-shapedinductance, whereby the position of said conductive body may be changedwith respect to said inductance.

2. A tuning arrangement for electric oscillations comprising anoscillatory circuit, a metallic generally U-shaped inductance havingparallel sides and a cross bar provided with a noncircular apertureincluded in said oscillatory circuit, a non-circular insulating bodyfitting in said aperture to resist rotation while allowing slidingmovement, a cross bar supported on said body and extending across saidU-shaped in ductarrce from one parallel side to the other but out ofcontact with both said sides, a set screw rotatably attached. to saidinsulating body, and an insulating support having a thread enmeshed withsaid screw whereby rotation of said screw imparts sliding motion to saidinsulating body for adjusting said conductive body along the sides ofsaid U-shaped inductance.

WERNER PUHLMANN. ERICH GOSSEL.

